Electron tube structure



1952 D. F. DRIESCHMAN EI'AL 2,582,68

ELECTRON TUBE STRUCTURE 2 SHEETS-SHEET 1 Filed July 12, 1949 H m 0 u W Cw E M Huber? H Eaves ATTORNEY I Jan. 15, 1952 D. F. DRIESCHMAN EI'AL2,532,684

ELECTRON TUBE STRUCTURE Filed July 12, 1949 2 SHEETS-SHEET g INVENTORSDona/d E Drfiescbman Hubs/'7 /7. Eaves ATTORNEY Patented Jan. 1 5, 1952v ELECTRON TUBE STRUCTUiRE Donald F. Drieschman, Los Altos, and HubertH.

Eaves, Palo Alto, Calif., asslgnors to Eitel McCullough, Inc., SanBruno, Calif., a corporation of California Application is, 12, 1949,Serial No. 104,198

12 Claims. (Cl; 313-252) l Our invention relates to improvements in theconstruction of negative-grid type electron tubes. and moreparticularly, to power tetrodes.

It is among the objects of our invention to i provide an improvedtetrode for transmitting application such as modulator service.

Another object is to provide an electron tube of rugged construction,capable of withstanding heavy shocks without displacement'of the'electrodes.

A further object is to provide a tube with a simplified base structureand improved electrode supports.

A still further object is to provide an improved envelope constructionand sealing arrangement for enclosing the electrodes.

The invention possesses other objects and features of advantage, some ofwhich with the foregoing, will be set forth in the following descriptionof our invention. It is to be understood that we do not limit ourselvesto this disclosure of species of our invention, as we may adopt variantembodiments thereof within the scope of the claims.

' Referring to the drawings:

Figure 1 is a vertical sectional view of our tube; and

Figure2 is a bottom view of the same.

In terms of broad inclusion, our electron tube comprises an evacuatedenvelope containing concentric electrodes such as a cathode, anode andone or more grids, our improvements relating particularly to theenvelope construction and the electrode supp ting and terminalstructure. As embodied in a tetrode, the envelope preferably comprisestwo sections sealed together along a plane transverse to the tube axis,with the anode supported by the upper'section and the cathode, controlgrid and screen grid supported by the lower section. The anodesupporting lead on the upper section is preferably coaxial with theenvelope axis and terminal pins for the other electrodes are preferablyarranged .on the lower section to lie in a circle about the envelopeaxis. In our improved tube the lower envelope section comprises a moldedvitreous header in which the terminal pins and electrode supports aresealed, conductor means between the pins and supports being preferablysealed within the vitreous header. The cathode support is preferablysealed centrally of the header and the supports for the control grid andscreen grid are preferably sealed in circular formation about thecathode support, the grid mounts being preferably of conical shape withlegs connected to the respective supports.

The anode lead is preferably tubularand communicates with the interiorof the envelope to also provide the exhaust tubulation for the tube.

In greater detail and referring to the drawings, our improved electrontube, illustrated as a tetrode, comprises an envelope having an uppersection 2 and a lower section 3. The upper section comprises acup-shapedblank 4 of a vitreous material such as glass having sealed to its loweredge a metal ring 6 provided with an outtumed flange 1. The lowersection 3 comprises a vitreous header 9 forming the bottom wall of theenvelope and has sealed along its periphery a metal ring II with anouttumed flange l2 registering with flange l of the upper section.Header 8 is preferably molded in the desired shape, as by meltingpowdered glass in a graphite mold. By such molded glass techniquethe'vari'ous metal parts hereinafter described may -readi1y be sealed inplace during the molding operation. After the tube has been assembledthe envelope sections are sealed together by a braze I3 about theperiphery offlanges I and I2. V

In our tube the electrodes are of concentric cylindrical constructioncomprising a cathode ll, control grid l6, screen grid l1 and anode l8.The cup-shaped metal anode I 8 is supported from the upper envelopesection 2 by a lead I! extending coaxially with the axis of the tube.This lead is hollow and serves the dual function of providing aconductor for the anode and an exhaust tubulation for the envelope.Tubular body H- of the lead is sealed to the upper portion of glassblank 4 and has a suitable fitting 22 at its lower end for fastening tothe anode l8. 4 metallic extension 23 of the lead provides a connectionto the exhaust system and, after evacuation of the envelope, is pinchedoff by' compressing the walls of the tubing together at tip 24. Slots 26in the lead serve to retard heat flow from the anode to the glass seal.This improved anode lead structure removes the complications usuallyoccurring when .an exhaust tubulation is arranged at the base portion ofthe tube. In our tube the absence of such an exhaust tubulation at thebase materially simplifies the header structure.

The cathode I4, control grid l6 and screen grid I! are all mounted .onthe lower envelope section 3 so that these electrodes .may be accuratelyassembled and aligned prior to the putting on of the upper half of theenvelope. Cathode It comprises a cylinder of metal such as nickel,preferably cup-shaped, having an electron emissive coating such as thebarium-strontium oxide mixture commonly used for that purpose. The

preferably cup-shaped sealed centrally in the header 8, this supportbeing I with its lower portions embedded directly in the glass of theheader. The flange of support 21 carries a sleeve 28 which in turn isconnected to the cathode by an interposed sleeve 29. This latter sleeveis of thin metal having poor heat conductivity so as to thermallyisolatethe cathode from the header structure. A metal rod 30 connectedto the lower end of support 21 preferably projects out through thebottom of header 8 for the purpose of carrying heat out from the cathodesupporting structure. This center rod may be used as a.

cathode terminal, but in our preferred tube construction is used merelyas a cooling pin.

Cathode i4 is heated by a suitable heater 3| mounted within the cathodecylinder. This heater is preferably a coil of insulated tungsten wirelying against the inner wall of the cathode,

- connected: at one end to the cathode cylinder and at the other end to"a central lead 32. An

- end plate 33 closing the lower end of the cathode cylinder serves toconserve heat and is insulated from the lead 32 by an insulator bushing34. Layers of corrugated sheets 36 at the top provide additional heatshielding and are preferably of a metal such as zirconium havinggettering or gas-absorbing properties, the upper end of the cathodebeing preferably recessed to retain these disks.

Control grid l6 and screen grid I! which surround the cathode arepreferably of the cage type, fabricated of suitable wire, and aresupported at their lower ends from the header structure. The controlgrid supports 31, say three in number, are arranged in a circle aboutthe cathode support. These supports are sealed in the header and projectupwardly into the envelope to carry the control grid mount 38, thelatter being preferably conical in shape and having three legs connectedto outturned ends of the supports 31. In a like manner a plurality ofscreen grid supports 39 are sealed in the header in a larger circlesurrounding the cathode support and spaced alternately with respect tothe control grid supports; The conical mount 4| for the screen grid haslegs connected to the supports 39,

' which legs lie between those of the control grid mount. This structureprovides arugged mounting for the grids and reduces the capacitanceeffects between the grid supports.

Four terminal pins 42, 43, 44 and 45 are sealed in the header to projectdownwardly frorr he envelope and are arranged ,in a circle abou. he tubeaxis, the upper ends of these pins being embedded in the glass of theheader. The interconnections between the terminal. pins .and electrodesupports are preferably sealed wholly within the glass of the header tofurther enhance the compactnessand ruggedness of the base structure.Thus the cathode pin 42 is connected to the rod 30 by a strap 46, thecontrol grid pin 43 is connected to one of the supports 31 by a strap41, and the'screen grid pin 44 is connected-to one of the supports 39 bya strap 48, which straps are embedded in the glass of the header. A post49 connected to the header pin 45 projects upwardly within the envelopeto support the outtumed end center rod 32, the latter extendin through aslot' Sl in cathode supporting sleeve 28. The various terminal pins andelectrode supports which are sealed in the header are preferably moldeddirectly to the glass when the header is formed in the mold. For thispurpose the graphite mold is shaped to hold the ring u and other metalparts in proper position. Powdered glass is then poured in the mold andall .is brought up to the melting point of the glass maining electrodeson the header section, the

two sections of the envelope are fitted together and brazed at It alongthe abutting flanges.

We claim:

1. An electron tube comprising an envelope having amolded vitreousheader at the lower end, concentric electrodes in the envelope includinga cathode and grid, a support for the cathode sealed centrally in theheader and projecting upwardly into the envelope, and supports for thegrid sealed in the header in circular formation about the cathodesupport and pro- Jecting upwardly into the envelope, a conical mount forthe'grid having diverging end portions connected to said grid supports,terminal pins for the electrodes sealed in the header and projectingdownwardly from the envelope, and means connecting the pins to therespective electrode supports.

2. An electron tube comprising an envelope having a molded vitreousheader at the lower end, concentric electrodes in the envelope includinga cathode and control grid and screen grid, a support for the cathodesealed centrally in the header and projecting upwardly into theenvelope, supports for the control grid and screen grid sealed in theheader in circular formation about the cathode support and projectingupwardly. into the envelope, the circle defined by the screen gridsupports being larger than that of the control grid supports, terminalpins for the electrodes sealed in the header and projecting downwardlyfrom the envelope, and means connecting the pins to the respectiveelectrode supports.-

3. An electron tube comprising an envelope having a molded vitreousheader at the lower end, concentric electrodes in the envelope includinga cathode and control grid and screen grid, a support for the cathodesealed centrally control grid supports, a conical mount for the controlgrid having diverging end portions connected to the control gridsupports, a conical mount for the screen grid having diverging endportions connected to the screen grid supports. terminal pins for theelectrodes sealed in the header and projectingdownwardly from theenvelope, and means connecting the pins to the respective electrodesupports.

4. An electron tube comprising an envelope having a molded vitreousheader at the lower end, concentric electrodes in the envelope includinga cathode, a support for the cathode comprising a cup having its lowerportion sealed centrally in the header, said cup penetrating onlypartially into the header, and a sleeve connecting the cathode to theflange of said cup.

5. An electron tube comprising an envelope having a molded vitreousheader at the lower end.

concentric electrodes in the envelope including a cathode and grid, asupport for the cathode comprising a cup having its lower portionssealed centrally in the header, a sleeve connecting the cathode to theflange of said cup, supports for the grid sealed in the header incircular formation about the cathode support and projecting upwardlyinto the envelope, and a conical mount for the grid having legsconnected to said grid supports.

6. An electron tube comprising an envelope having a molded vitreousheader at the lower end, concentric electrodes in the envelope includinga cathode and control grid and screen grid, a support for the cathodecomprising a cup having its lower portion sealed centrally in theheader, a sleeve connecting the cathode to the flange of said cup,supports for the control grid and screen grid sealed in the header incircular formation about the cathode support and projecting upwardlyinto the envelope, a conical mount for the control grid having legsconnected to the control grid supports, and a conical mount for thescreen grid having legs connected to the screen grid supports.

7. An electron tube comprising an envelope having upper and lowersections, the lower section having a molded vitreous header forming thebottom wall of the envelope, concentric electrodes in the envelopeincluding an anode and cathode and grid, terminal pins and supports forthe cathode and grid sealed in the header, and a lead for the anodesealed to the upper envelope section, the anode lead being coaxial withthe envelope axis and said cathode and grid terminal pins being locatedin the circle about said axis,

said supports for the grid being located in a circle of differentdiameter than that of the terminal pins.

8. An electron tube comprising an envelope having a vitreous header atthe lower end, concircle defined by the screen grid supports is thelargest.

9. An electron tube comprising an envelope having a vitreous upperportion, concentric electrodes in the envelope including an anode, and atubular metallic lead extending coaxially of the electrodes through theenvelope for supporting the anode, the vitreous upper portion of theenvelope being fused to the side walls of the tubular anode leadintermediate the ends of said lead, the lead providing a conductor forthe anode and also communicating with the interior of the envelope toprovide an exhaust tubulation, the outer end of the lead having its sidewalls compressed together to close the tubulation.

10. An electron tube comprising an envelope having a vitreous upperportion, concentric electrodes in the envelope including an anode, atubular metallic lead extending coaxially of the electrodes through theenve the anode, the vitreous upper por velope being fused to the sidewalls of the tubular anode lead intermediate the ends of said lead, thelead providing a conductor for the anode and also communicating with theinterior of the envelope to provide an exhaust tubulation, the outer endof the lead having its side walls compressed together to close thetubulation, a cap across the upper end of the anode, and meansconnecting the anode cap to the inner end of said lead.

11. An electron tube comprising an envelope having upper and lowersections joined together in a plane transverse to the axis of theenvelope, concentric electrodes in the envelope including an anode, atubular metallic lead perpendicular to said plane and extending throughthe upper section for supporting the anode, said upper envelope sectionbeing connected to the side walls of the tubular anode lead intermediatethe ends of said lead, the lead providing a conductor for the anode andalso communicating with the interior of the envelope to provide anexhaust tubulation, the outer end of the lead having its side wallscompressed together to close the tubulation, and means on the lowerenvelope section for supporting others of said electrodes.

12. A tetrode' comprising an envelope having upper and lower sectionsjoined together in a plane transverse to the envelope, concentricelectrodes in the envelope including an anode and cathode and controlgrid and screen grid, a tubular metallic lead perpendicular to saidplane and extending through the upper section for supporting the anode,said upper envelope section being connected to the side walls of thetubular anode lead intermediate the ends of said lead, the leadproviding a conductor for the anode and also communicating with theinterior of the envelope to provide an exhaust tubulation, the outer endof the lead having its side walls compressed together to close thetubulation, and means on the lower envelope section for supporting thecathode and control grid and screen grid.

DONALD F. DRIESCHMAN. HUBERT H. EAVES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Dorgelg Aug. 9, 1949

